Environmental carcinogens of the polynuclear aromatic hydrocarbon class such as benzo(a)pyrene (B(a)P) are metabolized by cellular enzyme systems to highly reactive bay region diol epoxides which have been identified as ultimate carcinogens. However, among the isomeric bay region diol epoxides of B(a)P chemical reactivity does not correlate with carcinogenicity, suggesting that interaction with biological systems modulates chemical reactivities in important ways. In fact, diol epoxides generated in vivo or applied to intact cells do not react with all potential cellular nucleophiles but show a high selectivity of adduct formation with cellular macromolecules. In general, in vivo selectivity patterns are modified, sometimes drastically, when diol epoxides react with purified macromolecules. I purpose to study the influence of chromatin structure on the covalent binding of several B(a)P-diol epoxides to DNA and histone proteins. I will attempt to find conditions where specificities observed with chromatin subunits (chromatosomes and core particles) duplicate specificities observed in vivo. This minimal system will then be dissected to obtain information as to which elements of the structure are important in the various specificities observed. These studies will look at several aspects of non-covalent interactions also (e.g. intercalation, DNA-induced detoxification). The analysis of both DNA and histone binding will be done by HPLC, thus speeding up analysis time significantly over present methods. To begin to study the possible effects of histone modification by diol epoxides on chromatin structure and function, the methods developed above will allow the preparation of a single histone, e.g. H3, which is highly enriched in adducts. This will be used to reconstitute chromatin with all other components unmodified. This chromatin will be compared with a control reconstitute by a variety of biochemical and biophysical methods.